Add @nospecialize to showarg

Author: timholy

src/OffsetArrays.jl

@@ -373,7 +373,7 @@ function Base.inds2string(inds::Tuple{Vararg{Union{IdOffsetRange, IdentityUnitRa
 end
 Base.showindices(io::IO, ind1::IdOffsetRange, inds::IdOffsetRange...) = Base.showindices(io, map(UnitRange, (ind1, inds...))...)
 
-function Base.showarg(io::IO, a::OffsetArray, toplevel)
+function Base.showarg(io::IO, @nospecialize(a::OffsetArray), toplevel)
     print(io, "OffsetArray(")
     Base.showarg(io, parent(a), false)
     Base.showindices(io, axes(a)...)

src/axes.jl

@@ -178,3 +178,10 @@ if VERSION < v"1.5.2"
     @inline Base.compute_offset1(parent, stride1::Integer, dims::Tuple{Int}, inds::Tuple{IdOffsetRange}, I::Tuple) =
         Base.compute_linindex(parent, I) - stride1*first(inds[1])
 end
+
+# This was deemed "too private" to extend: see issue #184
+# # Fixes an inference failure in Base.mapfirst!
+# # Test: A = OffsetArray(rand(4,4), (-3,5)); R = similar(A, (1:1, 6:9)); maximum!(R, A)
+# if isdefined(Base, :_firstslice)
+#     Base._firstslice(i::IdOffsetRange) = IdOffsetRange(Base._firstslice(i.parent), i.offset)
+# end